Impact extrusion lubricants



United States Patent 3,252,909 IMPACT EXTRUSION LUBRICANTS Richard H. Jenks, Sauquoit, N.Y., assignor to Revere Copper and Brass Incorporated, Rome, N.Y., a corporation of Maryland No Drawing. Filed June 6, 1963, Ser. No. 285,872

5 Claims. (Cl. 25237) This invention relates to impact extrusion lubricants for aluminum and aluminum alloys.

Impact or cold extrusion is the term applied to the process wherein a punch strikes an unheated metal slug in a confining die to form the metal into a desired shape or product. The metal flow may be between the punch and the walls of a closed die or through an opening formedin the die, and the metal slug may be either a solid shape if the finished extrusion is to be closed at one end or it maybe pierced (i.e. formed with a central opening) if the finished extrusion is to be open at both ends.

The impact extrusion process is used to form thin wall containers of aluminum and aluminum alloys, such as beer cans, collapsible toothpaste tubes and many other such products. Internal stresses developed in the aluminum metal slug being subjected to impact extrusion are very great, and the production of thin wall containers would not be possible unless friction between the surface of the metal and the surfaces of the punch and die is reduced to a minim-um. Lubricants employed to reduce the friction between these metal surfaces must meet stringent requirements. Specifically, these lubricants must be able to withstand the severe service conditions to which they are subjected during the extrusion operation, and the lubricant should not leave any residue or film on the surface of the finished extrusion that will contaminate the materials with which the container is ultimately to be filled or that will interfere with subsequent processing (e.g. painting) of the extrusion. Moreover,

1 the surface of the finished extrusion should be free of black (carbonized) areas and streaks, and preferably the lubricant should be capable of being removed from the surface of the extrusion without extensive cleaning operations. As a practical matter, the lubricant should be capable of being substantially completely removed from the surface of the aluminum extrusion by heating the extrusion to a temperature sufiicient to vaporize or burn off the lubricant film without leaving any black stain or carbonaceous residue of the finished extrusion.

Conventional lubricating oils are unsatisfactory impact extrusion lubricants in that they tend to break down or ignite under the severe surface conditions encountered and leave incompatible oily films and adherent carbonaceous residues on the surface of the finished extrusions. Moreover the lubricants heretofore commonly used in impact extrusion processes such as zinc stearate, lanolin or waxy formulations (e.g. paraflin) leave undesirable residues on the surface of finished aluminum extrusions that can not readily be removed without excessive cost that make the extrusions unacceptable for many purposes.

Aluminum containers made by impact extrusion may be divided into two general categories, each of which requires the use of an extrusion lubricant having certain special characteristics. The first category includes aluminum containers that are not intentionally annealed after being made or extruded, or are softened by heat as little as possible in order to maintain as much strength as possible. Aerosol cans and beer cans in which internal pressure is developed when used are examples of the type of container that would fall into this category. The second category includes those containers that after being extruded are annealed in order to facilitate squeezing or collapse of the container in order to force the contents thereof from the container. Collapsible toothpaste tubes are an example of the type of container that would fall into the second category of extruded aluminum containers. The present invention relates to lubricants for extruded aluminum containers of the last-mentioned category.

The impact extrusion of aluminum containers having very thin walls, for example, collapsible tooth paste tubes and the like, requires the use of an extrusion lubricant that will not break down or decompose under the extremely severe conditions of heat and pressure encountered in the impact extrusion operation. Thus, I have found that impact extrusion lubricants which perform well when used to make extrusions of the first of the aforementioned categories do not perform satisfactorily when used to make extrusions of the second of the aforementioned categories due to breakdown of the lubricant and formation of undesirable black stains and smutty residues on the surface of the extrusion. Moreover, I have found that conventional lubricants which can withstand the severe surface conditions encountered in the second category of extrusion operations cannot readily be removed from the surface of the extrusion or form adherent carbonaceous residues when the finished extrusion is heated to above its annealing temperature.

After an extensive investigation in which over '700 different compounds and compositions of matter were subjected to laboratory and commercial production tests to determine their utility as lubricants for the second category of extrusions, I have found that certain compositions of matter comprising a homogeneous mixture of at least one saturated monohydric aliphatic alcohol containing 14 or more, and preferably from 14 to 30 carbon atoms and at least one aliphatic compound selected from the group consisting of saturated monocarboxylic aliphatic acids containing 14 or more, and preferably from 14 to 30 carbon atoms, and the esters and salts of said acids permit the extrusion of extremely thin walled aluminum containers such as tooth paste tubes and the like, and these lubricant compositions are substantially completely removed from the surface of the finished extrusion when the extrusions are heated to above the annealing temperature of aluminum without undesirable streaking of the surface of the extrusion.

Alcohols are hydroxyl derivatives of hydrocarbons, and those alcohols derived from saturated aliphatic hydrocarbons are termed saturated aliphatic alcohols. These alcohols have the general formula (C 'H QOH, and the term saturated monohydric aliphatic alcohols as employed herein refers not only to straight chain alcohols having this formula but also to all isomers of the primary alcohols having the same formula. Similarly, the carboxyl derivatives of saturated aliphatic hydrocarbons having the general formula (C H )'COO I-I are termed saturated monocarboxylic aliphatic acids, and as employed herein this term refers not only to straight chain monocarboxylic acids but'also to all isomers of the primary acids having the same formula. The saturated monohydric aliphatic alcohols suitable for use as one of the essential constituents of my new lubricant formulation and the saturated monocarboxylic aliphatic acids and the salts and esters of these acids suitable for use as the other of the essential constituents thereof are those which are derived from saturated aliphatic hydrocarbons containing at least 14 carbon atoms, and preferably from 14 and 30 carbon atoms. These alcohols, acids, salts and esters are normally solid materials (i.e. they are solid at normal room temperature) and I have found that when formed into a homogeneous mixture in accordance with my in vention they have excellent extrusion lubricating properties when applied in the form of a thin dry film to the surface of an aluminum slug being subjected'to impact extrusion. Moreover, I have found that the already good lubricating properties of the homogeneous mixtures of higher aliphatic alcohols with higher aliphatic acids, salts and esters are improved by incorporating in the lubricant formulation up to about 10%, and preferably between about 4 and 10%, by weight of dibutyl ammonium tetrafiuoroborate.

The lubricant composition comprising a homogeneous mixture of one or more of the higher saturated monohydric aliphatic alcohols, and preferably between 30 and 95% by weight-of the aliphatic alcohols, one or more higher saturated monocarboxylic aliphatic acids, esters and/or salts, and'preferably between 5 and 70% by weight of the higher acids, salts or esters, and optionally up to by Weight of dibutyl ammonium tetrafluoroborate may be applied to the surface of the aluminum slug to be extruded by tumbling the slug in a fine powder of the lubricant composition. Alternatively, the lubricant can be applied to the slug by melting the composition and immersing the slug therein or spraying the molten composition on to the slug. Preferably, however, the lubricant composition is dissolved in a volatile solvent such as isopropyl alcohol or other volatile solvent for the particular composition, followed by immersing the metal slug in the lubricant solution and then, after removing the metal slug from the solution, allowing the volatile solvent to evaporate therefrom to leave the desired thin film of dry lubricant composition on the surface of the slug. Aluminum metal slugs thus coated with a dry film of my new lubricant composition can be formed into extremely thin-walled containers of the collapsible tube type without the lubricant breaking down or leaving undesirable black residues or streaks on the surface of the finished extrusion. Moreover, when the extrusion is heated to above the annealing temperature of aluminum (i.e., above about 480 F.), to anneal the aluminum to its dead soft condition, the residual lubricant film is substantially completely removed from the surface of the extrusion without forming adherent tarry or carbonaceous residues that render the extrusion unacceptable.

The following examples are illustrative but not limitative of the impact extrusion lubricants of my invention:

Example I One part (or about 9.09%) by weight of zinc stearate and 10 parts (or about 90.9%) by weight of stearyl alcohol were thoroughly mixed together to form a homogeneous lubricant composition in accordance with my invention. A thin layer of this lubricant composition was applied to the surfaces of a pierced aluminum slug by tumbling the slug in the powdery mixture. The coated slug was then subjected to impact extrusion to form the tubular shell of a collapsible toothpaste tube, and the extrusion was heated to 1000 F. to anneal the aluminum to its dead soft condition. The resulting extrusion of a clean, extremely thin-Walled annealed aluminum container having no black streaks or carbonaceous residues on the surface thereof.

Example 11 The same procedure as described in Example I was repeated with a lubricant composition formulated from one part (or about 50%) by weight of stearyl alcohol and one part (or about 50%) by Weight of behenic acid. After extrusion and annealing, the resulting thin-walled container had no black streaks or carbonaceous residues on the surface thereof.

Example 111 The same procedure as described in Example I was repeated with a lubricant composition formulated from one part (or about 33.3%) by weight of stearyl alcohol, one part (or about 33.3%) by weight of zinc stearate and one part (or about 33.3%) by weight of beeswax. After extrusion and annealing, the resulting collapsible tooth- 4 paste shell had no black streaks or carbonaceous residue on the surface thereof.

Example IV The same procedure as described in Example I was repeated with lubricants formulated from myristal alcohol, cetyl alcohol, stearyl alcohol, ceryl alcohol, melissyl alcohol, behenic acid, myricyl palmitate, zinc stearate, magnesium palmitate, paraffin, beeswax and dibutyl ammonium tetrafluoroborate, the individual lubricant formulations, containing between 30 and by weight of one or more of the higher aliphatic alcohols, between 5 and 70% by weight of one or more of the higher aliphatic acids, esters and salts and up to 10% by weight of dibutyl ammonium tetrafluoroborate. In each case, after coating a pierced aluminum slug with the lubricant composition and after extrusion and annealing of the aluminum extrusion, the resulting thin-walled aluminum container was free of black streaks and carbonaceous residues on the surface thereof.

I claim:

1. An impact extrusion lubricant for metal slugs of aluminum and aluminum alloys that are heated to above the annealing temperature of aluminum after impact extrusion thereof, said lubricant comprising essentially a homogeneous mixture of (a) between about 30 and 95% by weight of at least one saturated monohydric aliphatic alcohol containing from 14 to 30 carbon atoms, and (b) between about 5 and 70% by weight of at least one aliphatic compound selected from the group consisting of saturated monocarboxylic aliphatic acids containing from 14 to 30 carbon atoms and the :myricyl alcohol esters and Group II metal salts of said aliphatic acids. 2. An impact extrusion lubricant for metal slugs of aluminum and aluminum alloys that are heated to above the annealing temperature of aluminum after the extru-- sion thereof, said lubricant comprising essentially a homogeneous mixture of (a) between about 30 and 95 by weight of at least one saturated monohydric aliphatic alcohol containing from 14 to 30 carbon atoms,

(b) between about 5 and 70% by weight of at least one aliphatic compound selected from the group consisting of saturated monocarboxylic aliphatic acids containing from 14 to 30 carbon atoms and the myricyl alcohol esters and Group II metal salts of said aliphatic acids, and

(0) between about 4 to 10% by weight of dibutyl ammonium tetrafiuoroborate.

3. An impact extrusion lubricant for aluminum and aluminum alloys comprising a homogeneous mixture of about 91% .by weight of stearyl alcohol and about 9% by weight of zinc stearate.

4. An impact extrusion lubricant for aluminum and aluminum alloys comprising a homogeneous mixture of about 50% by weight of stearyl alcohol and about 50% by weight of behenic acid.

5. An impact extrusion lubricant for aluminum and aluminum alloys comprising a homogeneous mixture of about 33.3% by weight of stearyl alcohol, about 33.3% by weight of zinc stearate and about 33.3% by weight of beeswax.

References Cited by the Examiner UNITED STATES PATENTS 2,094,127 9/ 1937 Lazier 252-52 2,605,224 7/1952 Jahn 252-52 X OTHER REFERENCES Metalworking Lubricants, by Bastian, McGraw-Hill Book Co., Inc., New York, 1951, pages 101-105.

DANIEL E. WYMAN,P1-iinary Examiner. 

2. AN IMPACT EXTRUSION LUBRICANT FOR METAL SLUGS OF ALUMINUM AND ALUMINUM ALLOYS THAT ARE HEATED TO ABOVE THE ANNEALING TEMPERATURE OF ALUMINUM AFTER THE EXTRUSION THEREOF, SAID LUBRICANT COMPRISING ESSENTIALLY A HOMOGENEOUS MIXTURE OF (A) BETWEEN ABOUT 30 AND 95% BY WEIGHT OF AT LEAST ONE SATURATED MONOHYDRIC ALIPHATIC ALCOHOL CONTAINING FROM 14 TO 30 CARBON ATOMS, (B) BETWEEN ABOUT 5 AND 70% BY WEIGHT OF AT LEAST ONE ALIPHATIC COMPOUND SELECTED FROM THE GROUP CONSISTING OF SATURATED MONOCARBOXYLIC ALIPHATIC ACIDS CONTAINING FROM 14 TO 30 CARBON ATOMS AND THE MYRICYL ALCOHOL ESTERS AND GROUP II METAL SALTS OF SAID ALIPHATIC ACIDS, AND (C) BETWEEN ABOUT 4 TO 10% BY WEIGHT OF DIBUTYL AMMONIUM TETRAFLUOROBORATE.
 5. AN IMPACT EXTRUSION LUBRICANT FOR ALUMINUM AND ALUMINUM ALLOYS COMPRISING A HOMOGENOUS MIXTURE OF ABOUT 33.3% BY WEIGHT OF STEARYL ALCOHOL, ABOUT 33.3% BY WEIGHT OF ZINC STEARATE AND ABOUT 33.3% BY WEIGHT OF BEESWAX. 